BCAB #1785 - Occupancy Classification and Party Wall Construction Requirements

June 16, 2016

BCAB #1785

Re: Occupancy Classification and Party Wall Construction Requirements for Detached Garages and Detached Garages with Dwelling Units Above, Articles 9.10.2.1., 9.10.11.1. and 9.10.11.2.

Project Description

The project consists of 4 attached residential townhouse units, each unit located on its own fee simple parcel of land. The units are vertically fire separated from one another by party walls which are not constructed as firewalls as permitted by Article 9.10.11.2.  There are two detached storage garage buildings located in the rear yard(s) of the townhouse units.  Each storage garage building serves two townhouses and straddles those units’ common property line. This results in ½ of a storage garage building being located on each individual unit’s parcel of land. One of the storage garage buildings also includes a dwelling unit above each half of the building, however the storage garage does not serve the dwelling unit above, but rather serves the townhouse units detached from it.

Reason for Appeal

The local authority has determined that the party walls within the detached storage garage buildings are required to be constructed as a fire wall.  For the detached storage garage building with dwelling units above, additionally the dwelling units must be separated by a rated fire separation from the storage garage below.

Appellant's Position

The appellant contends that the detached storage garages are buildings of residential occupancy and the permission of Sentence 9.10.11.2.(1) is applicable and the party wall may be constructed as a 1 hour fire separation.   Similar units in the same development have garages attached to the individual residential dwelling units and in those cases the party wall is not required to be constructed as a fire wall.  The buildings with detached garages do not represent a higher level of risk and should be subject to the same requirements.

Local Authority’s Position

The building official maintains that the detached garages are buildings of low hazard industrial occupancy and not buildings of residential occupancy and that Sentence 9.10.11.2.(1) is not applicable.   Therefore, the party wall in the detached garages must be constructed as a fire wall.

In the storage garage building with dwelling units above, the storage garages do not serve the dwelling units below so they cannot be considered as part of the dwelling unit as permitted by 9.10.9.16.(3).  The building official considers the building(s) to be of mixed use and requires the appropriate horizontal fire separations between the storage garage and dwelling unit above.  The party wall must be constructed as a firewall.

Appeal Board Decision #1785

It is the determination of the Board that the garages in question are subsidiary to the detached dwelling units of residential occupancy that they serve.  In the storage garage building that does not have dwelling units above, the party wall need not be constructed as a firewall as permitted by Sentence 9.10.11.2.(1).

Further, for the building containing storage garages and dwelling units above, the party wall must be constructed as a firewall.  The floor assembly between the garage and the dwelling unit must be constructed with a 1 hour fire resistance rating in accordance with Sentence 9.10.9.16.(2).

Reason for Decision

As each individual storage garage serves only the dwelling unit on the same property, each storage garage is considered to be part of the dwelling unit it serves.   Table 9.10.2.1. indicates F3, Low­hazard industrial occupancies, does not include storage garages serving individual dwelling units).  This note is not specific to attached garages.  This is consistent with Appeal #1693.

In the storage garage building that does not have dwelling units above, each storage garage is considered a part of the detached dwelling unit it serves.   There is no dwelling unit above another dwelling unit, and therefore the permission of Sentence 9.10.11.2.(1) is applicable.

In the building containing storage garages and separate dwelling units above, each storage garage is considered a part of the detached dwelling unit it serves.  This results in a dwelling unit above another dwelling unit, and therefore the permission of Sentence 9.10.11.2.(1) is not applicable.  The requirements of Article 9.10.9.16. apply to all storage garages.

BCAB 1785 Site Plan (PDF)

Lyle Kuhnert, Chair, Building Code Appeal Board